Inverted telephoto type wide angle lens

ABSTRACT

An inverted telephoto type wide angle lens comprises, in succession from the object side, a divergent first group, a diaphragm-forward convergent second group and a diaphragm-rearward convergent third group. The first group includes a positive meniscus lens having its convex surface facing the object side, and three negative meniscus lenses having their convex surfaces facing the object side. The second group includes two positive lenses, a negative meniscus lens having its convex surface facing the object side, and a positive lens. The third group includes a positive meniscus having its convex surface facing the image side, a doublet biconcave negative lens and two positive lenses. The lens system satisfies certain conditions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an inverted telephoto type or so-called retrofocus type great aperture ratio ultra-wide angle lens having an aperture ratio number F2 and an angle of view of the order of 94°.

2. Description of the Prior Art

Generally, in a retrofocus type lens having a great aperture ratio, the wider the angle of view, the more pronounced the aggravation of the off-axis asymmetrical aberration such as coma and the resultant image, even though good in the central portion thereof, shows a conspicuous image flow in the radial directions or in the direction of concentric circles, particularly in the marginal portion of the picture plane, and moreover, presents much flare which tends to lead to a poor contrast. Accordingly, to improve the quality of image in the marginal portion, it is indispensable to eliminate coma which causes flare. However, there are two types of coma, i.e., m coma which is the coma in the meridional plane and S coma which is the coma in the sagittal direction, and when one of these comas is not corrected, the resultant image becomes an image of poor contrast accompanying flare, but S coma is extremely slower in the movement at the aberration correcting stage than m coma and it is therefore difficult to correct S coma and thus, it has been regarded as difficult to develop a great aperture ratio wide angle lens which presents lesser flare. Heretofore, in view of the above-noted difficulty, use has been made of means such as preponderantly correcting the m coma which is easier to correct or employing a non-spherical surface.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a wide angle lens which comprises spherical surfaces alone and in which various aberrations are well corrected and the coma in the sagittal is reduced and which enables an image of good contrast over the entire picture plane.

The invention will become fully apparent from the following detailed description thereof taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 2 and 3 show the lens arrangements of a first, a second and a third embodiment, respectively, of the present invention.

FIGS. 4, 5 and 6 show various aberrations at f=1.0 in the first, the second and the third embodiments, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will hereinafter be described with respect to a first embodiment thereof shown in FIG. 1. As shown, the construction of the present invention comprises three groups. That is, a first group A is a divergent group of negative refractive power as a whole, a second group B is a diaphragm-forward convergent group of positive refractive power as a whole, and a third group C is a diaphragm-rearward convergent group of positive refractive power as a whole. Further, the first group A comprises, in succession from the object side, a positive lens L₁ and three continuous negative meniscus lenses L₂, L₃, L₄ each having its convex surface facing the object side, the second group B comprises, in succession from the object side, lenses L₅, L₆ of small power, a negative meniscus lens L₇ having its convex surface facing the object side, and a positive lens L₈, and the third group C comprises, in succession from the object side, a positive lens L₉, a doublet negative lens L₁₀ and two positive lenses L₁₁, L₁₂. The diaphragm is provided between the second group B and the third group C. This lens system satisfies the following conditions (I) to (III):

    d.sub.21 +d.sub.22 >0.5f                                   (I)

    d.sub.19 >d.sub.20                                         (II)

    0.45R.sub.15 <R.sub.16 <0.73R.sub.15                       (III)

where f is the total focal length of the entire system, (d₂₁ +d₂₂) is the center thickness of the lens forming the doublet biconcave negative lens L₁₀ in the third group C, d₁₉ is the center thickness of the positive lens L₉ in the third group C, d₂₀ is the air space between the positive lens L₉ and the negative lens L₁₀ in the third group C, and R₁₅ and R₁₆ are the curvature radii of the surfaces of the negative meniscus lens L₇ in the second group B which are adjacent to the object side and the image side, respectively.

As previously described, it is difficult to correct S coma after the basic construction of the lens has been determined, because the movement at the aberration correcting stage is small. Generally, occurrence of remarkable S coma is seen in an extremely compacted lens system or a lens system in which the burden of aberration correction is concentrated upon a particular lens. Thus, S coma tends to increase in a lens type which bears an unreasonably great burden or aberration correction. Accordingly, to design a great aperture ratio lens system of high performance, it is necessary to examine the amount of occurrence of S coma from the basic construction study stage at which the lens type is chosen and to know that there is no unreasonableness in the type. A retrofocus type lens system, like the present invention, not only has a positive power simply for providing a predetermined focal length but also has a negative power for possessing a predetermined back focal length, and at the same time is imparted a positive power for negating the negative power. Usually, almost all of these positive powers are concentrated on the convergent groups. Accordingly, the convergent groups of a retrofocus type lens system must suppress occurrence of aberrations while having a strong power and thus, bear dual burden. From this, it is no exaggeration to say that the construction of the convergent groups almost determines the possibility of providing a great aperture ratio.

In the present invention, a sufficient length of the optical path of the diaphragm-rearward convergent group C is secured by virtue of condition (I), whereby the correction of spherical aberration and the various aberrations created by the divergent first group A can be reasonably effected to minimize m coma and S coma. In FIG. 1, the light ray from the infinity object point on the axis passing through the negative lens L₁₀ of the third group C becomes approximately parallel to the optical axis and therefore, even if the lens thickness is made great, it will in no way adversely affect the spherical aberration, etc. Where d₂₁ +d₂₂ is less than the lower limit of condition (I), it is difficult to correct spherical aberration and S coma while well correcting other off-axis aberrations and particularly, not only distortion is under-corrected but also flare results from increased m coma, and it is difficult to provide a great aperture ratio. To suppress the flare particularly resulting from excessively great spherical aberration of g-line (wavelength λ=435.8 nm), it is desirable that in the doublet negative lens L₁₀ of the third group C, ν₁₀ >ν₁₀ ' and 1.4f>|R₂₂ |>0.7f, where ν₁₀ and ν₁₀ ' are the refractive indices of the cemented lenses which are adjacent to the object side and the image side of the cemented surface, and R₂₂ is the curvature radius of the convex cemented surface facing the image side. Next, condition (II) is the condition for making compatible the correction of the spherical aberration and the correction of the image plane which are closely related to coma and eliminating the flare resulting from the curvature of image field which is liable to increase from the center of the picture plane to the marginal portion of the picture plane. When condition (II) is not satisfied, spherical aberration is under-corrected or, even if spherical aberration is corrected, the image plane is over-corrected to make it difficult for the image plane correction and the spherical aberration correction to be compatible. Further, to reduce the burden of the divergent first group A and suppress the occurrence of aberrations, the negative lens L₇ is disposed as a part of a negative power in the forward convergent second group B within the range of condition (III), thereby securing a predetermined back focal length. This negative lens L₇ is relatively near the diaphragm and therefore does not so much affect the distortion. When the upper limit of condition (III) is departed from, it is difficult to secure a predetermined back focal length and, when the lower limit of condition (III) is departed from, the jump-up of light rays at the surface R₁₆ of the negative lens L₇ which is concave to the image side becomes too intense and brings about remarkable occurrence of spherical aberration. This negative lens L₇ has the effect of suppressing the bending of lateral chromatic aberration and therefore, even if it is a negative lens, it is desirable that the Abbe number ν₇ thereof the ν₇ >40. Also, the cemented surface of the negative lens L₁₀ in the third group C should desirably be convex toward the image side in order to well maintain the lateral chromatic aberration.

A second embodiment shown in FIG. 2 is one in which the joined surfaces of the sixth lens L₆ are eliminated to decrease the number of surfaces of the lenses and improve the productivity. A third embodiment shown in FIG. 3 is one in which the air lens between the fifth and sixth lenses L₅ and L₆ of small power is eliminated to reduce the air contact surface which may cause ghost.

Various numeral data of each embodiment will be shown below. In the tables below, R₁, R₂, R₃, . . . , R₂₇ represent the curvature radii of the successive lens surfaces in order from the object side, d₁, d₂, d₃, . . . , d₂₆ represent the intervals betweeen the successive lens surfaces, and nd and νd represent the refractive indices and Abbe numbers, respectively, of the successive lenses for d-line (wavelength λ=587.6 mm).

    ______________________________________                                         First embodiment:                                                              Total focal length of entire system f = 1.0,                                   Angle of view 2w = 94°, F-number 2.0                                    ______________________________________                                         R.sub.1 = d.sub.1                                                                              = 0.270  nd.sub.1                                                                            = 1.50137                                                                              νd.sub.1                                                                         = 56.5                              R.sub.2 = 10.292                                                                         d.sub.2                                                                              = 0.005                                                        R.sub.3 = 2.005                                                                          d.sub.3                                                                              = 0.074  nd.sub.2                                                                            = 1.78797                                                                              νd.sub.2                                                                         = 47.5                              R.sub.4 = 0.897                                                                          d.sub.4                                                                              = 0.181                                                        R.sub.5 = 1.313                                                                          d.sub.5                                                                              = 0.074  nd.sub.3                                                                            = 1.78797                                                                              νd.sub.3                                                                         = 47.5                              R.sub.6 = 0.875                                                                          d.sub.6                                                                              = 0.172                                                        R.sub.7 = 1.792                                                                          d.sub.7                                                                              = 0.074  nd.sub.4                                                                            = 1.7481                                                                               νd.sub.4                                                                         = 52.2                              R.sub.8 = 1.141                                                                          d.sub.8                                                                              = 0.196                                                        R.sub.9 = -6.042                                                                         d.sub.9                                                                              = 0.064  nd.sub.5                                                                            = 1.80411                                                                              νd.sub.5                                                                         = 46.6                              R.sub.10 = 3.500                                                                         d.sub.10                                                                             = 0.191  nd.sub.5 '                                                                          = 1.59507                                                                              ν d.sub.5 '                                                                      = 35.6                              R.sub.11 = -2.714                                                                        d.sub.11                                                                             = 0.005                                                        R.sub.12 = 7.370                                                                         d.sub.12                                                                             = 0.382  nd.sub.6                                                                            = 1.75692                                                                              νd.sub.6                                                                         = 31.7                              R.sub.13 = -3.922                                                                        d.sub.13                                                                             = 0.282  nd.sub.6 '                                                                          = 1.7481                                                                               νd.sub.6 '                                                                       = 52.2                              R.sub.14 = -36.208                                                                       d.sub.14                                                                             = 0.005                                                        R.sub.15 = 2.208                                                                         d.sub.15                                                                             = 0.054  nd.sub.7                                                                            = 1.6968                                                                               νd.sub.7                                                                         = 55.6                              R.sub.16 = 1.137                                                                         d.sub.16                                                                             = 0.108                                                        R.sub.17 = 1.127                                                                         d.sub.17                                                                             = 0.333  nd.sub.8                                                                            = 1.6228                                                                               νd.sub.8                                                                         = 56.9                              R.sub.18 = -1.843                                                                        d.sub.18                                                                             = 0.181                                                        R.sub.19 = -3.824                                                                        d.sub.19                                                                             = 0.157  nd.sub.9                                                                            = 1.72342                                                                              νd.sub.9                                                                         = 47.0                              R.sub.20 = -1.172                                                                        d.sub.20                                                                             = 0.075                                                        R.sub.21 = -0.877                                                                        d.sub.21                                                                             = 0.346  nd.sub.10                                                                           = 1.713 νd.sub.10                                                                        = 53.9                              R.sub.22 = -0.809                                                                        d.sub.22                                                                             = 0.228  nd.sub.10 '                                                                         = 1.79504                                                                              νd.sub.10 '                                                                      = 28.4                              R.sub.23 = 2.760                                                                         d.sub.23                                                                             = 0.076                                                        R.sub.24 = -8.761                                                                        d.sub.24                                                                             = 0.186  nd.sub.11                                                                           = 1.79668                                                                              νd.sub.11                                                                        = 45.4                              R.sub.25 = -1.186                                                                        d.sub.25                                                                             = 0.005                                                        R.sub.26 = 3.257                                                                         d.sub.26                                                                             = 0.221  nd.sub.12                                                                           = 1.50032                                                                              νd.sub.12                                                                        = 81.9                              R.sub.27 = -2.499                                                              Back focal length Bf = 1.844                                                   ______________________________________                                         Second Embodiment:                                                             Total focal length of entire system f = 1.0,                                   Angle of view 2w = 94°, F-number 2.0                                    ______________________________________                                         R.sub.1 = d.sub.1                                                                              = 0.270  nd.sub.1                                                                            = 1.50137                                                                              νd.sub.1                                                                         = 56.5                              R.sub.2 = 10.292                                                                         d.sub.2                                                                              = 0.005                                                        R.sub.3 = 2.020                                                                          d.sub.3                                                                              = 0.074  nd.sub.2                                                                            = 1.78797                                                                              νd.sub.2                                                                         = 47.5                              R.sub.4 = 0.897                                                                          d.sub.4                                                                              = 0.181                                                        R.sub.5 = 1.313                                                                          d.sub.5                                                                              = 0.074  nd.sub.3                                                                            = 1.78797                                                                              νd.sub.3                                                                         = 47.5                              R.sub.6 = 0.875                                                                          d.sub.6                                                                              = 0.172                                                        R.sub.7 = 1.792                                                                          d.sub.7                                                                              = 0.074  nd.sub.4                                                                            = 1.74629                                                                              νd.sub.4                                                                         = 52.3                              R.sub.8 = 1.141                                                                          d.sub.8                                                                              = 0.196                                                        R.sub.9 = -6.042                                                                         d.sub.9                                                                              = 0.064  nd.sub.5                                                                            = 1.80218                                                                              νd.sub.5                                                                         = 46.6                              R.sub.10 = 4.337                                                                         d.sub.10                                                                             = 0.191  nd.sub.5 '                                                                          = 1.59507                                                                              νd.sub.5 '                                                                       = 35.6                              R.sub.11 = -2.637                                                                        d.sub.11                                                                             = 0.017                                                        R.sub.12 = 17.304                                                                        d.sub.12                                                                             = 0.696  nd.sub.6                                                                            = 1.7552                                                                               νd.sub.6                                                                         = 27.5                              R.sub.14 = -8.824                                                                        d.sub.14                                                                             = 0.005                                                        R.sub.15 = 2.127                                                                         d.sub.15                                                                             = 0.054  nd.sub.7                                                                            = 1.6968                                                                               νd.sub.7                                                                         = 55.6                              R.sub.16 = 1.147                                                                         d.sub.16                                                                             = 0.103                                                        R.sub.17 = 1.137                                                                         d.sub.17                                                                             = 0.333  nd.sub.8                                                                            = 1.6223                                                                               νd.sub.8                                                                         = 53.1                              R.sub.18 =  -1.985                                                                       d.sub.18                                                                             = 0.142                                                        R.sub.19 = -3.824                                                                        d.sub.19                                                                             = 0.123  nd.sub.9                                                                            = 1.72342                                                                               d.sub.9                                                                            = 38.0                              R.sub.20 = -1.261                                                                        d.sub.20                                                                             = 0.083                                                        R.sub.21 = -0.940                                                                        d.sub.21                                                                             = 0.431  nd.sub.10                                                                           = 1.713 νd.sub.10                                                                        = 53.9                              R.sub.22 = -0.900                                                                        d.sub.22                                                                             = 0.162  nd.sub.10 '                                                                         = 1.79504                                                                               d.sub.10 '                                                                         = 28.4                              R.sub.23 = 2.463                                                                         d.sub.23                                                                             = 0.076                                                        R.sub.24 = -8.761                                                                        d.sub.24                                                                             = 0.186  nd.sub.11                                                                           = 1.76684                                                                              νd.sub.11                                                                        = 45.4                              R.sub.25 = -1.191                                                                        d.sub.25                                                                             = 0.005                                                        R.sub.26 = 3.152                                                                         d.sub.26                                                                             = 0.228  nd.sub.12                                                                           = 1.50032                                                                              νd.sub.12                                                                        = 81.9                              R.sub.27 = -2.279                                                              Back focal length Bf = 1.853                                                   (R.sub.13, d.sub.13, nd.sub.6 ', and νd.sub.6 ' are missing                 ______________________________________                                         numbers)                                                                       Third Embodiment:                                                              Total focal length of entire system f =  1.0,                                  Angle of view 2w = 940, F-number 2.0                                           ______________________________________                                         R.sub.1  =  3.284                                                                        d.sub.1                                                                              = 0.196  nd.sub.1                                                                            = 1.6172                                                                               νd.sub.1                                                                         = 54.0                              R.sub.2 = 8.018                                                                          d.sub.2                                                                              = 0.005                                                        R.sub.3 = 2.026                                                                          d.sub.3                                                                              = 0.093  nd.sub.2                                                                            = 1.79877                                                                              νd.sub.2                                                                         = 44.3                              R.sub.4 = 0.980                                                                          d.sub.4                                                                              = 0.108                                                        R.sub.5 = 1.181                                                                          d.sub.5                                                                              = 0.078  nd.sub.3                                                                            = 1.79877                                                                              νd.sub.3                                                                         = 44.3                              R.sub.6 = 0.858                                                                          d.sub.6                                                                              = 0.184                                                        R.sub.7 = 1.934                                                                          d.sub.7                                                                              = 0.088  nd.sub.4                                                                            = 1.74443                                                                              νd.sub.4                                                                         = 49.4                              R.sub.8 = 1.121                                                                          d.sub.8                                                                              = 0.187                                                        R.sub.9 = 271.649                                                                        d.sub.9                                                                              = 0.074  nd.sub.5                                                                            = 1.79877                                                                              νd.sub.5                                                                         = 44.3                              R.sub.10 = 1.074                                                                         d.sub.10                                                                             = 0.882  nd.sub.5 '                                                                          = 1.58144                                                                              νd.sub.5 '                                                                       = 40.8                              R.sub.14 = -2.589                                                                        d.sub.14                                                                             =  0.005                                                       R.sub.15 = 1.412                                                                         d.sub.15                                                                             = 0.064  nd.sub.7                                                                            = 1.6968                                                                               νd.sub.7                                                                         = 55.6                              R.sub.16 = 0.926                                                                         d.sub.16                                                                             = 0.103                                                        R.sub.17 = 1.076                                                                         d.sub.17                                                                             = 0.309  nd.sub.8                                                                            = 1.60562                                                                              νd.sub.8                                                                         = 43.9                              R.sub.18 = -10.455                                                                       d.sub.18                                                                             = 0.103                                                        R.sub.19 = -49.020                                                                       d.sub.19                                                                             = 0.240  nd.sub.9                                                                            = 1.75692                                                                              νd.sub.9                                                                         = 31.7                              R.sub.20 = -1.287                                                                        d.sub.20                                                                             = 0.093                                                        R.sub.21 = -1.065                                                                        d.sub.21                                                                             = 0.534  nd.sub.10                                                                           = 1.713  d.sub.10                                                                           = 53.9                              R.sub.22 = -0.940                                                                        d.sub.22                                                                             = 0.039  nd.sub.10 '                                                                         = 1.80518                                                                               d.sub.10 '                                                                         = 25.5                              R.sub.23 = 2.428                                                                         d.sub.23                                                                             = 0.078                                                        R.sub.24 = -11.176                                                                       d.sub.24                                                                             = 0.167  nd.sub.11                                                                           = 1.713 νd.sub.11                                                                        = 53.9                              R.sub.25 = -1.181                                                                        d.sub.25                                                                             = 0.005                                                        R.sub.26 = 6.029                                                                         d.sub.26                                                                             = 0.176  nd.sub.12                                                                           = 1.60311                                                                              νd.sub.12                                                                        = 60.7                              R.sub.27 = -2.194                                                              Back focal length Bf = 1.931                                                   (R.sub.11 -R.sub.13, d.sub.11 -d.sub.13, nd.sub.6, nd.sub.6 ',                 νd.sub.6 and νd.sub.6 ' are missing                                      numbers).                                                                      ______________________________________                                    

The various aberrations in the respective embodiments are shown in FIGS. 4, 5 and 6, respectively. From these Figures, it is seen that in spite of the fact that the great aperture ratio ultra-wide angle lens according to the present invention comprises spherical surfaces alone, various aberrations including coma are well corrected. 

I claim:
 1. An inverted telephoto type wide angle lens comprising, in succession from the object side, a divergent first group (A) including a positive meniscus lens (L₁) having its convex surface facing the object side, and negative meniscus lenses (L₂ -L₄) having their convex surfaces facing the object side; a diaphragm-forward convergent second group (B) including positive lenses (L₅, L₆), a positive lens (L₈) and a negative meniscus lens (L₇) disposed between said positive lenses (L₅, L₆) and said positive lens (L₈) and having its convex surface facing the object side; and a diaphragm-rearward convergent third group (C) including a positive meniscus lens (L₉) having its convex surface facing the image side, positive lenses (L₁₁, L₁₂) and a doublet biconcave negative lens (L₁₀) disposed between said positive meniscus lens (L₉) and said positive lenses (L₁₁, L₁₂); said inverted telephoto type wide angle lens satisfying the following conditions:

    d.sub.21 +d.sub.22 >0.5f                                   (I)

    d.sub.19 >d.sub.20                                         (II)

    0.45R.sub.15 <R.sub.16 <0.73R.sub.15                       (III)

where f is the total focal length of the entire system, (d₂₁ +d₂₂) is the center thickness of the lens forming the biconcave negative lens (L₁₀) in said third group (C), d₁₉ is the center thickness of the positive meniscus lens (L₉) in said third group (C), d₂₀ is the air space between the positive meniscus lens (L₉) and the negative lens (L₁₀) in said third group (C), and R₁₅ and R₁₆ are the curvature radii of the surfaces of the negative lens (L₇) in said second group (B) which are adjacent to the object side and the image side, respectively.
 2. An inverted telephoto type wide angle lens according to claim 1, wherein numerical data are as follows:

    ______________________________________                                         Total focal length of entire system f = 1.0,                                   Angle of view 2w = 94°, F-number 2.0                                    ______________________________________                                         R.sub.1  =  3.431                                                                        d.sub.1                                                                              = 0.270  nd.sub.1                                                                            = 1.50137                                                                              νd.sub.1                                                                         = 56.5                              R.sub.2 = 10.292                                                                         d.sub.2                                                                              = 0.005                                                        R.sub.3 = 2.005                                                                          d.sub.3                                                                              = 0.074  nd.sub.2                                                                            = 1.78797                                                                              νd.sub.2                                                                         = 47.5                              R.sub.4 = 0.897                                                                          d.sub.4                                                                              = 0.181                                                        R.sub.5 = 1.313                                                                          d.sub.5                                                                              = 0.074  nd.sub.3                                                                            = 1.78797                                                                              νd.sub.3                                                                         = 47.5                              R.sub.6 = 0.875                                                                          d.sub.6                                                                              = 0.172                                                        R.sub.7 = 1.792                                                                          d.sub.7                                                                              = 0.074  nd.sub.4                                                                            = 1.7481                                                                               νd.sub.4                                                                         = 52.2                              R.sub.8 = 1.141                                                                          d.sub.8                                                                              = 0.196                                                        R.sub.9 = -6.042                                                                         d.sub.9                                                                              = 0.064  nd.sub.5                                                                            = 1.80411                                                                              νd.sub.5                                                                         = 46.6                              R.sub.10 = 3.500                                                                         d.sub.10                                                                             = 0.191  nd.sub.5 '                                                                          = 1.59507                                                                              νd.sub.5 '                                                                       = 35.6                              R.sub.11 = -2.714                                                                        d.sub.11                                                                             = 0.005                                                        R.sub.12 = 7.370                                                                         d.sub.12                                                                             = 0.382  nd.sub.6                                                                            = 1.75692                                                                              νd.sub.6                                                                         = 31.7                              R.sub.13 = -3.922                                                                        d.sub.13                                                                             = 0.282  nd.sub.6 '                                                                          = 1.7481                                                                               νd.sub.6 '                                                                       = 52.2                              R.sub.14 = -36.208                                                                       d.sub.14                                                                             = 0.005                                                        R.sub.15 = 2.208                                                                         d.sub.15                                                                             = 0.054  nd.sub.7                                                                            = 1.6968                                                                               νd.sub.7                                                                         = 55.6                              R.sub.16 = 1.137                                                                         d.sub.16                                                                             = 0.108                                                        R.sub.17 = 1.127                                                                         d.sub.17                                                                             = 0.333  nd.sub.8                                                                            = 1.6228                                                                               νd.sub.8                                                                         = 56.9                              R.sub.18 = -1.843                                                                        d.sub.18                                                                             = 0.181                                                        R.sub.19 = -3.824                                                                        d.sub.19                                                                             = 0.157  nd.sub.9                                                                            = 1.72342                                                                              νd.sub.9                                                                         = 47.0                              R.sub.20 = -1.172                                                                        d.sub.20                                                                             = 0.075                                                        R.sub.21 = -0.877                                                                        d.sub.21                                                                             = 0.346  nd.sub.10                                                                           = 1.713  d.sub.10                                                                           = 53.9                              R.sub.22 = -0.809                                                                        d.sub.22                                                                             =  0.228 nd.sub.10 '                                                                         = 1.79504                                                                               d.sub.10 '                                                                         = 28.4                              R.sub.23 = 2.760                                                                         d.sub.23                                                                             = 0.076                                                        R.sub.24 = -8.761                                                                        d.sub.24                                                                             = 0.186  nd.sub.11                                                                           = 1.79668                                                                              νd.sub.11                                                                        = 45.4                              R.sub.25 = -1.186                                                                        d.sub.25                                                                             = 0.005                                                        R.sub.26 = 3.257                                                                         d.sub.26                                                                             = 0.221  nd.sub.12                                                                           = 1.50032                                                                              νd.sub.12                                                                        = 81.9                              R.sub.27 = -2.499                                                              Back focal length Bf = 1.844                                                   ______________________________________                                    

where R₁, R₂, R₃, . . . , R₂₇ represent the curvature radii of the successive lens surfaces in order from the object side, d₁, d₂, d₃, . . . , d₂₆ represent the intervals between the successive lens surfaces, and nd and νd represent the refractive indices and Abbe numbers, respectively, of the successive lenses for d-line (wavelength λ=587.6 nm).
 3. An inverted telephoto type wide angle lens according to claim 1, wherein numerical data are as follows:

    ______________________________________                                         Total focal length of entire system f = 1.0,                                   Angle of view 2w = 94°, F-number 2.0                                    ______________________________________                                         R.sub.1  =  3.431                                                                        d.sub.1                                                                              = 0.270  nd.sub.1                                                                            = 1.50137                                                                              νd.sub.1                                                                         = 56.5                              R.sub.2 = 10.292                                                                         d.sub.2                                                                              = 0.005                                                        R.sub.3 = 2.020                                                                          d.sub.3                                                                              = 0.074  nd.sub.2                                                                            = 1.78797                                                                              νd.sub.2                                                                         = 47.5                              R.sub.4 = 0.897                                                                          d.sub.4                                                                              = 0.181                                                        R.sub.5 = 1.313                                                                          d.sub.5                                                                              = 0.074  nd.sub.3                                                                            = 1.78797                                                                              νd.sub.3                                                                         = 47.5                              R.sub.6 = 0.875                                                                          d.sub.6                                                                              = 0.172                                                        R.sub.7 = 1.792                                                                          d.sub.7                                                                              = 0.074  nd.sub.4                                                                            = 1.74629                                                                              νd.sub.4                                                                         = 52.3                              R.sub.8 = 1.141                                                                          d.sub.8                                                                              = 0.196                                                        R.sub.9 = -6.042                                                                         d.sub.9                                                                              = 0.064  nd.sub.5                                                                            = 1.80218                                                                              νd.sub.5                                                                         = 46.6                              R.sub.10 = 4.337                                                                         d.sub.10                                                                             = 0.191  nd.sub.5 '                                                                          = 1.59507                                                                              νd.sub.5 '                                                                       = 35.6                              R.sub.11 = -2.637                                                                        d.sub.11                                                                             = 0.017                                                        R.sub.12 = 17.304                                                                        d.sub.12                                                                             = 0.696  nd.sub.6                                                                            = 1.7552                                                                               νd.sub.6                                                                         = 27.5                              R.sub.14 = -8.824                                                                        d.sub.14                                                                             = 0.005                                                        R.sub.15 = 2.127                                                                         d.sub.15                                                                             = 0.054  nd.sub.7                                                                            = 1.6968                                                                               νd.sub.7                                                                         = 55.6                              R.sub.16 = 1.147                                                                         d.sub.16                                                                             = 0.103                                                        R.sub.17 = 1.137                                                                         d.sub.17                                                                             = 0.333  nd.sub.8                                                                            = 1.6223                                                                               νd.sub.8                                                                         = 53.1                              R.sub.18 = -1.985                                                                        d.sub.18                                                                             = 0.142                                                        R.sub.19 = -3.824                                                                        d.sub.19                                                                             = 0.123  nd.sub.9                                                                            = 1.72342                                                                              νd.sub.9                                                                         = 38.0                              R.sub.20 = -1.261                                                                        d.sub.20                                                                             = 0.083                                                        R.sub.21 = -0.940                                                                        d.sub.21                                                                             = 0.431  nd.sub.10                                                                           = 1.713  d.sub.10                                                                           = 53.9                              R.sub.22 = -0.900                                                                        d.sub.22                                                                             = 0.162  nd.sub.10 '                                                                         = 1.79504                                                                               d.sub.10 '                                                                         = 28.4                              R.sub.23 = 2.463                                                                         d.sub.23                                                                             =  0.076                                                       R.sub.24 = -8.761                                                                        d.sub.24                                                                             = 0.186  nd.sub.11                                                                           = 1.76684                                                                              νd.sub.11                                                                        = 45.4                              R.sub.25 = -1.191                                                                        d.sub.25                                                                             = 0.005                                                        R.sub.26 = 3.152                                                                         d.sub.26                                                                             = 0.228  nd.sub.12                                                                           = 1.50032                                                                              νd.sub.12                                                                        = 81.9                              R.sub.27 = -2.279                                                              Back focal length Bf = 1.853                                                   (R.sub.13, d.sub.13, nd.sub.6 ', and νd.sub.6 ' are missing                 ______________________________________                                         numbers)                                                                  

where R₁, R₂, R₃, . . . , R₂₇ represent the curvature radii of the successive lens surfaces in order from the object side, d₁, d₂, d₃, . . . d₂₆ represent the intervals between the successive lens surfaces, and nd and νd represent the refractive indices and Abbe numbers, respectively, of the successive lenses for d-line (wavelength λ=587.6 nm).
 4. An inverted telephoto type wide angle lens according to claim 1, wherein numerical data are as follows:

    ______________________________________                                         Total focal length of entire system f = 1.0,                                   Angle of view 2w = 94°, F-number 2.0                                    ______________________________________                                         R.sub.1  =  3.284                                                                        d.sub.1                                                                              = 0.196  nd.sub.1                                                                            = 1.6172                                                                               νd.sub.1                                                                         = 54.0                              R.sub.2 = 8.018                                                                          d.sub.2                                                                              = 0.005                                                        R.sub.3 = 2.026                                                                          d.sub.3                                                                              = 0.093  nd.sub.2                                                                            = 1.79877                                                                              νd.sub.2                                                                         = 44.3                              R.sub.4 = 0.980                                                                          d.sub.4                                                                              = 0.108                                                        R.sub.5 = 1.181                                                                          d.sub.5                                                                              = 0.078  nd.sub.3                                                                            = 1.79877                                                                              νd.sub.3                                                                         = 44.3                              R.sub.6 = 0.858                                                                          d.sub.6                                                                              = 0.184                                                        R.sub.7 = 1.934                                                                          d.sub.7                                                                              = 0.088  nd.sub.4                                                                            = 1.74443                                                                              νd.sub.4                                                                         = 49.4                              R.sub.8 = 1.121                                                                          d.sub.8                                                                              = 0.187                                                        R.sub.9 = 271.649                                                                        d.sub.9                                                                              = 0.074  nd.sub.5                                                                            = 1.79877                                                                              νd.sub.5                                                                         = 44.3                              R.sub.10 = 1.074                                                                         d.sub.10                                                                             = 0.882  nd.sub.5 '                                                                          = 1.58144                                                                              νd.sub.5 '                                                                       = 40.8                              R.sub.14 = -2.589                                                                        d.sub.14                                                                             = 0.005                                                        R.sub.15 = 1.412                                                                         d.sub.15                                                                             = 0.064  nd.sub.7                                                                            = 1.6968                                                                               νd.sub.7                                                                         = 55.6                              R.sub.16 = 0.926                                                                         d.sub.16                                                                             = 0.103                                                        R.sub.17 = 1.076                                                                         d.sub.17                                                                             = 0.309  nd.sub.8                                                                            = 1.60562                                                                              νd.sub.8                                                                         = 43.9                              R.sub.18 = -10.455                                                                       d.sub.18                                                                             = 0.103                                                        R.sub.19 = -49.020                                                                       d.sub.19                                                                             = 0.240  nd.sub.9                                                                            = 1.75692                                                                              νd.sub.9                                                                         = 31.7                              R.sub.20 = -1.287                                                                        d.sub.20                                                                             = 0.093                                                        R.sub.21 = -1.065                                                                        d.sub.21                                                                             = 0.534  nd.sub.10                                                                           = 1.713 νd.sub.10                                                                        = 53.9                              R.sub.22 = -0.940                                                                        d.sub.22                                                                             = 0.039  nd.sub.10 '                                                                         = 1.80518                                                                              νd.sub.10 '                                                                      = 25.5                              R.sub.23 = 2.428                                                                         d.sub.23                                                                             = 0.078                                                        R.sub.24 = -11.176                                                                       d.sub.24                                                                             = 0.167  nd.sub.11                                                                           = 1.713 νd.sub.11                                                                        = 53.9                              R.sub.25 = -1.181                                                                        d.sub.25                                                                             =  0.005                                                       R.sub.26 = 6.029                                                                         d.sub.26                                                                             = 0.176  nd.sub.12                                                                           = 1.60311                                                                              νd.sub.12                                                                        = 60.7                              R.sub.27 = -2.194                                                              Back focal length Bf = 1.931                                                   (R.sub.11 -R.sub.13, d.sub.11 -d.sub.13, nd.sub.6, nd.sub.6 ',                 νd.sub.6 and νd.sub.6 ' are missing                                      numbers)                                                                       ______________________________________                                    

where R₁, R₂, R₃, . . . , R₂₇ represent the curvature radii of the successive lens surfaces in order from the object side, d₁, d₂, d₃, . . . , d₂₆ represent the intervals between the successive lens surfaces, and nd and νd represent the refractive indices and Abbe numbers, respectively, of the successive lenses for d-line (wavelength λ=587.6 nm). 